Follow-up tasks For more information on selection, planting,
After pruning, tie the trunk of each grapevine cultural practices, and environmental quality,
to the trellis wires with twine. Check young contact your local Iowa State University
grapevines periodically to make sure the twine Extension ofﬁce. If you want to learn more
is not girdling the trunk. Also, tie the dormant about horticulture through training and
fruiting canes to the wires near the end of each volunteer work, ask for information about
cane. the ISU Extension Master Gardener program.
Horticultural information also is available from
these Web sites.
Tools required to prune grapevines include
a hand shears, lopping shears, saw, a small
ISU Extension Distribution Center—
pocket scale to weigh the pruned material, ISU Horticulture—
and twine. Colored fabric strips also are www.yardandgarden.extension.iastate.edu
useful for marking fruiting canes.
Prepared by Richard Jauron, extension horticulturist,
and Diane Nelson, extension communication
File: Horticulture 2-3
Issued in furtherance of Cooperative Extension work,
Acts of May 8 and June 30, 1914 in cooperation with
the U.S. Department of Agriculture. Jack M. Payne,
director, Cooperative Extension Service, Iowa State
University of Science and Technology, Ames, Iowa.
… and justice for all
The U.S. Department of Agriculture (USDA) prohibits
discrimination in all its programs and activities on the
basis of race, color, national origin, gender, religion,
age, disability, political beliefs, sexual orientation,
and marital or family status. (Not all prohibited bases
apply to all programs.) Many materials can be made
available in alternative formats for ADA clients. To ﬁle
a complaint of discrimination, write USDA, Ofﬁce of
Civil Rights, Room 326-W, Whitten Building, 14th and
Independence Avenue, SW, Washington, DC 20250-
9410 or call 202-720-5964.
RG 502 Revised April 2007
Pruning grapes is easier when you understand shoots and ultimately the canes for next year’s tiﬁcation, some gardeners tie brightly colored
the growth and fruiting characteristics of the crop. strips of fabric to those canes they wish to retain.
Six-cane Knifﬁn system Leave equal numbers of renewal spurs (canes
Reasons for pruning This is similar except that it contains six fruit- pruned back to one or two buds). Remove all
Grapevines produce fruit clusters on the previ- ing canes on three trellis wires instead of four the other one-year-old canes. Next, weigh the
ous season’s growth (two-year and older wood canes on two wires. In addition, six one- or pruned canes. The weight of the canes is used
is not fruitful). Before pruning, an average two-bud renewal spurs are also retained. to determine the number of buds to retain on
grapevine may have 200 to 300 buds which are the grapevine.
capable of producing fruit. If the vine is left un-
pruned, the number of grape clusters would be To determine the number of buds to leave,
excessive. The vine would be unable to ripen the use the following balanced pruning formula:
large crop or sustain adequate vegetative growth. “30 plus 10.” For the ﬁrst pound of canes
1 Year Old removed, leave 30 buds. For each additional
The purpose of pruning is to obtain maximum Fruiting Canes pound, leave an additional 10 buds.
yields of high quality grapes and to allow adequate
vegetative growth for the following season. When counting the number of buds to be
retained, include the buds on the fruiting canes
Common training systems and also on the renewal spurs.
To maximize crop yield, grapevines are trained
to a speciﬁc system. The most common training The balanced pruning concept is illustrated in
systems used by home gardeners are the four- the following examples.
cane Knifﬁn and six-cane Knifﬁn.
If a grapevine had two pounds of canes
Four-cane Knifﬁn system removed at dormant pruning, the gardener
This system is popular because of its simplicity. would leave 30 buds for the ﬁrst pound of
After pruning, a grapevine trained to the four- canes, plus an additional 10 buds for a total of
cane Kniffen system consists of four fruiting 40 buds. Using the four-cane Knifﬁn system,
canes, two on each side of the trunk, trained the four fruiting canes would each have eight or
onto two trellis wires. In addition, four very Recommended pruning time nine buds. Four renewal spurs containing one
short canes (termed renewal spurs) are also The most desirable time to prune grapevines is or two buds also would be retained. The total
retained. The renewal spurs contain one or two in late winter or early spring. In Iowa, prun- number of buds should equal 40.
buds and are very important in the training ing can begin in late February and should be
system. The buds on the renewal spurs provide completed by early April. (Grapevines pruned If a vine had three pounds of canes removed,
at this time of year will bleed heavily. However, the grower should leave 30 buds for the ﬁrst
the bleeding will not harm the vines.) pound of canes, 10 for the second pound, plus
a ﬁnal 10 for the third pound, or a total of 50
Renewal Spurs 1 Year Old Balanced pruning
Fruiting Canes The degree or extent of pruning is dictated by
For the training systems common in Iowa,
vine vigor. Vine vigor is determined by weigh-
the maximum number of retained buds on a
ing the amount of pruned material.
grapevine is 60. If too many buds are present
after the initial pruning and weighing, remove
Start by selecting and retaining the appropriate
as many as needed to obtain the desired bud
number of fruiting canes per vine. To aid iden-